Study On The Accumulation, Degradation And Toxicity Of The Chiral Pesticide Sulfoxaflor In Tadpoles Of Rana Nigromaculat

Sulfoxaflor,a chiral pesticide,is the fourth-generation neonicotinoid insecticide,which can control a variety of piercing-sucking pests.Sulfoxaflor is considered the preferred pesticide for integrated pest control.At present,there are few studies on the stereoselective bioaccumulation-elimination behavior and toxic effects of sulfoxaflor in amphibians.In this paper,Rana nigromaculata tadpoles was used as an environmental carrier,the stereoselective bioaccumulation behavior and toxic effects of sulfoxaflor on R.nigromaculata tadpoles were studied.The main research contents and conclusions are as follows:1.The acute toxicity of sulfoxaflor to the R.nigromaculata tadpoles was studied.The LC50 value for 96-h acute toxicity of sulfoxaflor to tadpoles was 427.37 mg/L.The toxicity of sulfoxaflor to Gosner 26 stage tadpoles was low.The range of activities of the poisoned tadpoles was reduced,and the swimming activity was reduced.Tadpole intoxication was manifested by reduced range of motion,reduced activity,tail bending toward the head,and body turning sideways.2.The effects of antioxidant enzymes(SOD,CAT,GR),GST,ACh E enzyme activities,soluble protein,and MDA contents were studied in the R.nigromaculata tadpoles exposed to low,medium,and high concentrations(4.27,23.50,and 42.73 mg/L)of sulfoxaflor for 28 d.Compared with the control group,the antioxidant enzymes and GST detoxification enzymes of tadpoles were induced and activated by sulfoxaflor,ACh E enzyme was inhibited,and the MDA content was increased.This indicates that sulfoxaflor caused certain damage to the antioxidant defense system and nervous system of tadpoles.3.The effect of sulfoxaflor on the growth of R.nigromaculata tadpoles was investigated.After 28 d of exposure,compared with the control group,the body length reduced by 5.01%,7.09%,and 7.26%;tail length by 2.74%,7.96%,and 9.28%,respectively;the snout-to-vent length by 9.01%,11.21%,and 13.44%,respectively and body weight by 9.64%,9.90%,and 15.14% in the low,medium,and high concentration treatment groups,respectively.The data showed that sulfoxaflor had a certain inhibitory effect on the growth of R.nigromaculata tadpoles.The higher the exposure concentration,the more significant the inhibitory effect on the body length,tail length,snout-to-vent length,and body weight of tadpoles.4.The effects of TSH,TH,T3,and T4 contents and dio2、dio3、tra、trb genes the expression in R.nigromaculata tadpoles were studied after 28 d exposure to sulfoxaflor.Compared with the control group,sulfoxaflor increased the TSH and TH contents,and decreased T3 and T4 content in tadpoles;it elevated the expression of dio2、dio3、tra genes and decreased the expression of trb genes.This indicates that sulfoxaflor can interfere with the thyroid regulatory mechanism in the R.nigromaculata tadpoles.5.A liquid chromatography-tandem mass spectrometry(LC-MS/MS)method for the detection of four enantiomers of sulfoxaflor in R.nigromaculata tadpoles was established by CHIRALPAK IH-3 chiral column.The recoveries of sulfoxaflor enantiomers in in tadpoles were 78.47%-94.24%,the RSD was 1.38%-9.70%,and the matrix effect(ME%)was-23.72%-26.46%.The LOD and LOQ of(-)-2S,3Rsulfoxaflor and(+)-2R,3S-sulfoxaflor were 0.02 and 0.06 mg/kg,respectively.The LOD and LOQ of(-)-2R,3R-sulfoxaflor and(+)-2S,3S-sulfoxaflor were 0.03 and 0.09 mg/kg,respectively.The data showed that the accuracy and precision of the method met the requirements of pesticide residue analysis.6.The stereoselective bioaccumulation and elimination behavior of sulfoxaflor in R.nigromaculata tadpoles were studied.During the 28-d exposure period,the bioaccumulation of sulfoxaflor enantiomers in tadpoles was positively correlated with the magnitude of exposure;the EF(Enantiomer Fraction)values did not fluctuate significantly,and the EFA and EFB values of all treatment groups were within the fluctuation range of 0.5±0.02.During the 5-d elimination period,the elimination half-lives of sulfoxaflor enantiomer in all treatment groups were1.11-2.06 d,and the elimination rate was fast;the fluctuation of EF values were not significant,and the fluctuations range of EFA values and EFB values were 0.48-0.54.The study indicated that the bioaccumulation and elimination of sulfoxaflor enantiomers in R.nigromaculata tadpoles were not stereoselective.In this study,the bioaccumulation,and toxic effects of sulfoxaflor in the tadpoles of the R.nigromaculata tadpoles were investigated to provide a reference for evaluating the potential risks of the pesticide in amphibians and the ecological environment.